content: // Protocol Buffers - Google's data interchange format
  // Copyright 2008 Google Inc.  All rights reserved.
  // https://developers.google.com/protocol-buffers/
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //     * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //     * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //     * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  
  package com.google.protobuf;
  
  import static com.google.protobuf.ExtensionRegistryLite.EMPTY_REGISTRY_LITE;
  
  /**
   * A factory object to create instances of {@link ExtensionRegistryLite}.
   *
   * <p>
   * This factory detects (via reflection) if the full (non-Lite) protocol buffer libraries
   * are available, and if so, the instances returned are actually {@link ExtensionRegistry}.
   */
  final class ExtensionRegistryFactory {
  
    static final String FULL_REGISTRY_CLASS_NAME = "com.google.protobuf.ExtensionRegistry";
  
    /* Visible for Testing
       @Nullable */
    static final Class<?> EXTENSION_REGISTRY_CLASS = reflectExtensionRegistry();
  
    /* @Nullable */
    static Class<?> reflectExtensionRegistry() {
      try {
        return Class.forName(FULL_REGISTRY_CLASS_NAME);
      } catch (ClassNotFoundException e) {
        // The exception allocation is potentially expensive on Android (where it can be triggered
        // many times at start up). Is there a way to ameliorate this?
        return null;
      }
    }
  
    /** Construct a new, empty instance. */
    public static ExtensionRegistryLite create() {
      if (EXTENSION_REGISTRY_CLASS != null) {
        try {
          return invokeSubclassFactory("newInstance");
        } catch (Exception e) {
          // return a Lite registry.
        }
      }
      return new ExtensionRegistryLite();
    }
  
    /** Get the unmodifiable singleton empty instance. */
    public static ExtensionRegistryLite createEmpty() {
      if (EXTENSION_REGISTRY_CLASS != null) {
        try {
          return invokeSubclassFactory("getEmptyRegistry");
        } catch (Exception e) {
          // return a Lite registry.
        }
      }
      return EMPTY_REGISTRY_LITE;
    }
  
  
    static boolean isFullRegistry(ExtensionRegistryLite registry) {
      return EXTENSION_REGISTRY_CLASS != null
          && EXTENSION_REGISTRY_CLASS.isAssignableFrom(registry.getClass());
    }
  
    private static final ExtensionRegistryLite invokeSubclassFactory(String methodName)
        throws Exception {
      return (ExtensionRegistryLite) EXTENSION_REGISTRY_CLASS
          .getDeclaredMethod(methodName).invoke(null);
    }
  }
  